The present invention relates to a pneumatic tire containing a ply of knitting fabric as a reinforcement.
Hitherto, as a ply for a pneumatic tire such as a chafer, a bead filler or a carcass there has been generally employed a plane fabric or a cord fabric which is woven of warps of a tire cord arranged as a main reinforcing element and finer wefts than the warps. The wefts are roughly woven enough to maintain an arrangement of the warps and spaces between the warps.
Such a cord fabric or plane fabric is prepared as follows: the warps are arranged and shed alternately, e.g. when a warp is shed like upward, downward and upward, an adjacent warp is shed like downward, upward and downward. The weft is inserted through the series of the sheddings one after another by means of a shuttle and beaten to give the fabric.
In manufacturing a pneumatic tire, the cord fabric or the plane fabric is subjected to dipping treatment and topping treatment to prepare a ply. During the processes, however, there is a problem that the structure of the fabric is ready to be disturbed and to form a condition of so-called "slippage". Accordingly it is difficult to make the fabric rough when the density arrangement has increased too much.
For preventing the slippage of the fabric, there is proposed a method in which one weft is clamped by 2 or 3 warps to form a tire cord fabric. However, the method is complicated and requires high cost, which makes the productivity lower.
For reference, typical structures of the fabric used for conventional chafers are shown in Table 1.
TABLE 1 __________________________________________________________________________ Structure of chafer Density Cord Material (per 5 cm square) Use of tire __________________________________________________________________________ 840 d/l .times. 840 d/l Nylon (multiple filaments) 30 .times. 30 Tire for car and light truck 1260 d/l .times. 1260 d/l Nylon (multiple filaments) 31 .times. 31 Tire for truck and bus 450 d .times. 450 d Nylon (mono filament) 48 .times. 48 Radial tire for car 1100 d .times. 1100 d Nylon (mono filamant) 40 .times. 40 Tire for truck and light truck 20 yarn No. count/l .times. 20 yarn No. count/l Vinylon 54 .times. 54 Tire for motorcycle 20 yarn No. count/2 .times. 20 yarn No. count/2 Vinylon 54 .times.54 Tire for car and light __________________________________________________________________________ truck
In manufacturing a bias tire using the cord fabric prepared according to the above process, the following process is generally employed. That is, the cord fabrics are cut at an angle of 20.degree. to 70.degree. with respect to the direction of the warp arrangement included in the fabric. The cut fabrics are welded successively to give a ply. A cylindrical carcass is fabricated on a drum by the use of at least two plies in a manner where the warps in the ply cross the warps in the adjacent ply. Then, the carcass is formed into a toroidal tire.
With respect to the carcass prepared by the process described above, there occurr the following problems. First, since the warps are easy to move because of an insufficient fixing of the warps to the wefts in the above-mentioned process and the each space between the cords has a lack of uniformity, durability of the obtained tire is lowered. Second, the warps consisting in the cord fabric have a tendency to wave owing to their structural shape which causes the cord fabric to be rugged. Therefore, the thickness of the fabric is increased apparently so that for the purpose of covering the whole fabric, there is a necessity that the topping rubber is applied to the fabric in a large amount resulting in a thick rubber layer to inhibit a contact between the cords in the fabric. It is disadvantageous from the viewpoint of a weight of tire. Third, since the cord fabric is prepared by a weaving attended with shedding the warps, there is a limit with respect to the productivity. Further, it is necessary to select the materials for the warps and the wefts so that they do not slip on each other, and a long staple cannot be preferably used for the weft.
An object of the present invention is to provide a pneumatic tire which eliminates the above-mentioned problems, and is excellent in uniformity and durability and applicable to cars, light trucks, trucks, light vehicles such as motorcycles or bicycles, and the like.